fnord_disc over at EU managed to cobble together code that fits very closely to what WG uses to calculate penetration over distance, and recently released the source code for it (which @Captain_F22ACE improved upon, more on that below). I won't get into the specifics of the equation (feel free to read the reddit link below for that), and a lot of this data requires the ability to extract gameparams.data to obtain specific shell characteristics not listed in-game such as drag constant and krupp value.

Basically how to read the graph:

Pensacola/Indianapolis/New Orleans 203mm AP:

Blue line = raw penetration (what we are familiar with in WoT since shell arc is minor outside of derps and SPGs). Raw penetration assumes you hit a perfectly flat, 0 degree surface

Red line = penetration against the belt armor of the ship with vertical impact angle adjusted (but horizontally, e.x. player-controlled angling by turning the ship, still being 0)

Krupp is a balancing variable that provides a free penalty or bonus to penetration. It has no special behavior.

It's a scaling constant. It directly modifies all penetration values over distance.

If one shell has 2000 Krupp and another shell is exactly the same but has 2200 Krupp, then it will have 10% more penetration at any distance.

Also, @Captain_F22ACE improved upon this code. Added simulated penetration after striking an armor plate. I'll let him post the source code himself in case he doesn't want others to see

But it looks something like this (Iowa 16" SHS AP shell used for example, sorry for overlapping text because 14" laptop scaling on 1080P does screwy things)

^155mm thick plate used here btw (Mosvka belt armor), and also with scout plane + main battery +16% range module included so you can see where plunging fire starts to take effect. Gun elevation sadly never reaches full 45 degrees like it historically did, maxes out to 30 instead.

Distance is read in meters x 10^4, so "1.5" on the x-axis = 15km, "2" = 20km, and so on.

...

It's not perfect since shells of very low mass (76mm on Smith) tend to get quirky readings on the improved code for calculating energy left after hitting the first place (as ships do have multi-layered armor, so citadeling sometimes requires going through 3-4 plates of armor), but the raw penetration calculations are still relatively accurate:

^ 30mm plate used here btw, didn't set actual gun angle for this so range is iffy.

So yeah, have fun pouring over the graphs already there and seeing what is the optimal distance to engage a target.

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Interesting how, at the latter end of the shell's range, the penetration tends to improve. In actuality, would it not hit terminal velocity at some point, say, with something like the 127mm shells on US DDs with their rainbows?

Interesting how, at the latter end of the shell's range, the penetration tends to improve. In actuality, would it not hit terminal velocity at some point, say, with something like the 127mm shells on US DDs with their rainbows?

Terminal velocity normally applies to objects in free-fall with the forces of gravity and buoyancy balanced against each other with drag force being accounted as well. But I'd have to do some research if it'd actually apply or be significant with respect to ballistics. Technically it could, but instead of just moving in the Y direction, the shell is moving along an X,Y vector, and gravity only applies to the Y part of the vector. While drag is applied in the X,Y directions.

Also, I got things fixed with the graphs readability and the 2nd pen model. Will post it here in a few hours.